Help please

[Dan G]

Ok, it's been a while since I've been on, so I have accumulated my share of Jeep woes.

I installed a plow in early January at my brother's house 75 miles from home. On the way home, big yellow plow pushed all the air away from DSPO's 2 core radiator (YES, on a 360) and caused me to overheat 260+ deg F. Brother was kind enough to loan me trailer, buggy lugged plow into trailer (of course during the ONLY snow storm we had all year), and managed to make it home.

I purchased a new 4 core radiator and installed it, and what the heck took out the thermostat for good measure. Since that time, I've done my usual Home Depot runs without so much as a blip towards hot on the temp gauge.

Decided that since 'Running Hippo' is 'running sooo well' that I should take another long trip.

WELL, tranny won't go into third until I hit 60mph, used to happen at 40mph. 'RH' is still pushing lots o' heat, the temp gauge is telling me 240. Stop and go traffic makes gauge crawl towards 250.

Prequalifiers... engine is at 208K miles without a rebuild. I am at least 4th owner. Timing chain probably needs to be done desperately, rebuild needed in near future.

Question 1: Is overheating due to timing chain?

Question 2: Is tranny problem due to vacuum modulator (TF727)

Question 3: Does anyone want to buy a slightly rusted FSJ with a plow? She's dark blue with the 'light cordovan' interior...

[River Beast]

Check your fan clutch... sounds like it's not pulling the air through the radiator for cooling...also check the weep hole on the bottom of the snout of the waterpump for weepage. Your pump can be on it's way out as well....

Have you tried backflushing the system? You could have some crud built up in the water jackets in the block.

Can't help you on the 727.. I have a TH400..sorry

Don't sell it just because of this...get it fixed and be a proud FSJer!!!

[steven79]

#1 put a thermostat back in it (factory temp one) I think they were 195 degress,that will let the water sit in the rad long enough to cool off and let the clutch fan work proprly.
#2 tf727's don't have vac mods they use a cable to the carb for shift points. ;)

[Spinner]

How are your other shift points? If 1st & 2nd still shift at the previous points then you may have an internal problem with your tranny. What about manually shifting from 2nd to 3rd? Any probs there? If all of the shift points are now at higher mph/rpm, then you can adjust the shift linkage (looks like a Chebby kick-down linkage below your throttle linkage on the carb.). Tech section has a write-up on that procedure. Very important to set this shift linkage correctly or else you get much tranny clutch wear and much excess heat produced due to an over-revved motor. :eek:

[River Beast]

OOOPS!! I thought you meant you 'changed' out the the thermostat....yeah you need one for city driving for sure...

[J20fan]

I change out to 165* thermostat for the summer months. This keeps my engine temp at an excellent level in higher ambient temperatures. I also flush the system with a cooling system flush that removes scale etc. from the block.

[Dan G]

"Very important to set this shift linkage correctly or else you get much tranny clutch wear and much excess heat produced due to an over-revved motor."

Thanks Monster Mash!! Will do!

Also, will reinstall t-stat, though I might make a slight mod to it. Recently have been reading about adding a 1/8" hole to the flange of the t-stat to allow bypass if t-stat ever gets stuck.

Any thoughts??

[1BADJP]

Are you running a trans cooler or just the one in the radiator??
Install a HD trans cooler and run it through the radiator also.
try changing your trans fluid and filter--probably cooked fluid when overheated engine.
definitly check your fan clutch
You may need to install electric fan when plow is on to help cool radiator.
200,000 miles shouldn't be a problem if engine flow is good, look at flow in radiator while engine is running to see if it is flowing at all.
Do you know anyone with a laser temp gun??? they work real well and can pinpoint alot of system problems.
I wouldn't drill any holes in housing---if Jeep wanted one they would have put one!!!
GOOD LUCK

[Dan G]

Ok, reviving my old topic here...

1. I lubricated the TV linkage and readjusted it, tranny still operating poorly, won't go into 3rd until 60 and goes back in to 2nd shortly below 60.

2. 1BADJP, not drill hole in t-stat housing, drill hole in t-stat flange to allow a bit of bypass if element gets stuck. Has anyone done this?

3. 1BADJP, been looking for a reason to buy one of those laser temp guns. HVAC engineer by trade, maybe I can write it off as a 'work tool'!?!

4. Will changing out the valve body, fluid and filter cure my problem or am I in for a complete tranny rebuild.

5. If complete tranny rebuild, what's the going rate for a rebuild with the B&M manual shift valve body (2nd means 2nd and 1st means 1st) and HD clutches??

[gsmikie]

as for the trans shift point problem on the 727 there is a spring at the back of the intake that keeps tension on the linkage if the spring is gone/broken it will make the 3rd gear shift real late also the bushing in the kick down linkage at the bellhousing that holds the linkage cross shaft crack and fall out with age as for the over heat problem i would look at the fan clutch the lazer temp guns are cool as for the b&m man shift body and kevlar clutches and viton seals it runs about $600.00 for their kit

[ibnfe]

In my experiences on trannies, usually changing out the valve body with new will usually reveal all the other pending problems in the tranny. If you change the valve body and don't rebuild the tranny, you will probably need to within a short time. My 727 made it 'til 230,000 miles before everything started going south. As far as the rebuild goes, you can get all the consumable stuff for less than $250.00, and that includes a new converter. I do all of my own maintenance, so I can't help on how much it would cost to have someone else do it. Here's what the 727 tech manual says are probable causes for your delayed upshift: throttle linkage needs adjustment, kickdown band out of adjustment/worn/broke, worn seal rings, reaction shaft support rings worn, worn front clutch, governor problem. The first two are what I would concentate on first since they are easy and will avoid the rebuild if they work. Check/adjust your throttle linkage and the front band. If those and a fluid/filter change don't fix your problem, then it is internal somewhere.

[Wesdog]

Steven79 brought up the theory that:

[#1 put a thermostat back in it (factory temp one) I think they were 195 degress, that will let the water sit in the rad long enough to cool off and let the clutch fan work properly.]

*****************************************

There was a post a while back on the LT1edit list regarding the issue of flow rate through the radiator and I thought some on this list might be interested:

----------------------

According to Newton's law of forced convection, the amount of heat transferred can be represented as this:

Q=hA(Tw-Tr)

Where:
Q is the amount of heat in calories or BTM's or whatever unit you like.
h is the heat transfer coefficient for the system
A is the area of the surface where the heat transfer takes place and (Tw-Tr) is the difference in temperature between the coolant and the radiator (or the engine), i.e. delta T.

Nowhere does it mention the speed of convection. Because we're talking about identical setups except for flow, all the variables will be identical except for coolant temp. ***All that matters in determining how much heat is transferred is delta T, the difference in temperature between the coolant and the radiator.***

Let's look at two scenarios:

Scenario 1: 10 GPM coolant flow
Coolant temp coming out of the engine: 180 degrees
Ambient air temp: 100 degrees
Coolant temp as it comes out of the radiator: 120 degrees
Average delta T across radiator: 50 degrees

Scenario 2: 30 GPM coolant flow. Three times the flow, so the coolant is in the radiator 1/3 as long and loses only 1/3 as much temp per gallon:
Coolant temp coming out of the engine: 180 degrees
Ambient air temp: 100 degrees
Coolant temp as it comes out of the radiator: 160 degrees
Average delta T across radiator: 70 degrees

An average 70 degree difference vs. a 50 degree difference works out to 40% better heat transfer for the 30 gpm system, even though the drop in temp across the radiator is three times less than the 10 gpm system. Since the engine is going to be producing the same amount of waste heat in both cases, the delta T's for both systems must be the same. Therefore, for the second system, the coolant values would have to be 160 coming out of the engine and 140 coming out of the radiator. I realize it won't be exactly those values, but I'm not up to differential equations right now.

So despite the fact that the temperature drop across the radiator is less in the faster flowing system, you have 40% greater heat capacity for racing and on average your coolant temps will be lower. An added bonus is that because the coolant temp inside the engine is lower, you will be less prone to pinging and the computer will run more timing.

Now, why do you have to put a restrictor in the cooling system of an older smallblock to run without a thermostat? Well, it actually has nothing to do with thermodynamics, at least not directly. You can reference the faq at www.stewartcomponents.com (http://www.stewartcomponents.com) if you want to verify what I'm saying, but the short of it is this: The restrictor isn't there to regulate flow, it's there to regulate pressure. The radiator is on the high side of the pump on older systems, and as the pump pressure climbs with increased flow, it will eventually push the safety cap open, even though it's not boiling over, causing a gradual loss of coolant and eventual overheating when the pump starts cavitating. That's all. The LT1's system has been re-designed so the radiator is on the low side of the system and not subject to high pressure. The only reason you even need a restrictor is to hold the gasket in place for the water neck.

Sorry if I rubbed anyone the wrong way, but you've got to nip disinformation in the bud before it becomes an urban legend.

Stonebreaker
-------------------------------------

What's this mean as far as FSJ's are concerned? It appears the thermostat not only regulates the engine temp, it also helps regulate the pressure the radiator see at higher rpms. It's not there to slow down the flow through the radiator although the stock thermostat certainly is a significant restriction. I use a high flow style thermostat that is available at most speed shops and through PAW. It is available in 160, 180 and 195 temperatures. They all have a couple of small bypass holes drilled in the housing to allow a small amount of heated coolant to flow through the thermostat so it will open sooner as the engine reaches the setpoint temp. When they are fully open they allow a significantly larger volume of coolant to flow through the system to the radiator than the stock thermostat. This type thermostat is also of a higher quality and less prone to failure than the stock ones. Hope this was of value to the list.

[ August 28, 2002, 11:29 PM: Message edited by: Wesdog ]

[Al Johnson]

Wesdog, I just love it when the math confirms my gut feeling on how stuff works. Never made sense to me to slow the flow of coolant to make it cool better.
Thanks for showing us the facts!
Al

[krob725]

You don't need to drill a bypass hole because it has a bypass hose already there.

krob725

[fredws]

Scenario 1: 10 GPM coolant flow
Coolant temp coming out of the engine: 180 degrees
Ambient air temp: 100 degrees
Coolant temp as it comes out of the radiator: 120 degrees
Average delta T across radiator: 50 degrees

Scenario 2: 30 GPM coolant flow. Three times the flow, so the coolant is in the radiator 1/3 as long and loses only 1/3 as much temp per gallon:
Coolant temp coming out of the engine: 180 degrees
Ambient air temp: 100 degrees
Coolant temp as it comes out of the radiator: 160 degrees
Average delta T across radiator: 70 degrees

An average 70 degree difference vs. a 50 degree difference works out to 40% better heat transfer for the 30 gpm system, even though the drop in temp across the radiator is three times less than the 10 gpm system. Since the engine is going to be producing the same amount of waste heat in both cases, the delta T's for both systems must be the same. Therefore, for the second system, the coolant values would have to be 160 coming out of the engine and 140 coming out of the radiator. I realize it won't be exactly those values, but I'm not up to differential equations right now. Well, hate to bust Stonebreakers bubble, but. . . .

The heat transfer given in BTU/hr would be:

Q=M*Cp*deltaT

where Q is the heat transfer in BTU/hr
M is the flowrate, in GPM
Cp is 500 for water, of course with antifreeze it will be a bit different, but won't matter here as we are just compairing the two.
and of course deltaT is the difference in the entering and leaving fluild temp.

anyway, if you plug all that in for each case:

10*500*(180-120)=300,000 BTU/hr

30*500*(180-160)=300,000 BTU/hr

No difference.

[Wesdog]

Fredws, interesting info. I see that you list your occupation as a research engineer so I assume you have the background to know what you are talking about. I am not a degreed engineer but I read a lot and know a little about a lot of different fields. The bottom line appears the same to me regarding the need to slow down the flow through the system - it is not a valid concern at the flow rates involved. There is a problem of having to low of a flowrate and I assume there are upper flowrate limits that are constrained by allowable system pressure and the restriction to flow. The fluid used and its ability to absorb and release thermal energy as you pointed out is part of the equation. Thanks for taking the time to respond, I may have some fun with the data you provided. Where is the formula from? The guy who wrote that post I included knows his stuff. I know there is always more than one way to analyze this sort of situation and there are a lot of variables but my intuition tells me that the higher flow would have a higher efficiency and provide better heat transfer. I believe the pressure drop in the radiator also has a significant cooling effect so a high flow system needs a highflow/low restriction radiator to work properly. Ok enough of this for now. I'm going to do some brushing up on this to clear up some questions I have.

[fredws]

Wesdog, the equation is derived from the Bernoulli equation, of course modified to gpm instead of velocity, simple conservation of energy. But this of course is measuring the amount of energy removed from the fluid by the radiator. It is not the job of the thermostat to control the amount of heat rejected in the radiator, but instead to maintain a desired operating temperature in the engine.

but . . . back to the problem, no pun intended smile.gif , I would guess that he is not getting flow, since the radiator is new and there is no thermostat, I would think that there must be a hose collapsing somewhere or like RB said, block needs to be backflushed. The backflushing is a good idea either way, I do mine once a year just for good measure!

[jode]

Originally posted by Wesdog:
I believe the pressure drop in the radiator also has a significant cooling effect so a high flow system needs a highflow/low restriction radiator to work properly. If you are suggesting that the pressure drop helps cooling in the same way an A/C unit cools by dropping the pressure of the coolant in the condensor, then you believe incorrectly...the pressure in a automotive cooling system is there for one purpose...to keep the coolant from boiling...

BTW, on a separate note, let me throw out a little more A/C tech on here that may help to explain why a faster flowing coolant can cool more efficiently than a slower flowing one....
In a residential a/c system (for example) if the temperature difference (known as Delta T) between the incoming air and the outgoing air at the compressor unit is too high (ie, the air is getting heated up a lot) you would think at first that the unit was performing well and that it was really transferring a lot of heat to the air. This thought is incorrect, a high delta T means only one thing...the air flow is restricted....the reason an air flow restriction raises the delta T is because what little air that is going through the fins is moving slower and hence, is getting hotter. The problem is that, operating in this manner, the system is inefficient and will not provide enough cooling. Why? Because a little air that is super heated is not as effective as a lot of air that is only slightly heated...
its the same concept in the coolant system of a jeep...a little bit of super heated coolant passing through the fins will not take away as much heat from the engine as a higher volume of fluid that moves faster (and hence carries less heat per gallon)

So it all makes sense in my mind...did I explain that well enough that it makes sense in yours? tongue.gif

[fredws]

Jode, you got it! You have to look at the energy, not the temperature, there is a difference. So, it either does not have enough air flow across, or not enough coolant flow through.

[Dan G]

ok, enough of heat transfer

Fredws, you prove correctly that the BTUs removed is identical with different flows, but what everyone seems to be ignoring is the upper limit of the delta T.

Obviously, if I was at 260 deg F (assuming Jeep gauge and interpolation are correct), then I'm concerned about my returning water temperature almost more than I am about the heat rejected, because at too high a temp, the engine and tranny cook

[Rent-A-Cop]

they do make t-stats now that have a safty function(there is some sort of vavle that opens whent the t-stat goe shot) that prevents your engine from overheating and locking up, not sure how much they cost, seen it on a show on the speed channel a couple months back

[Wesdog]

Dan, I would be very concerned about my engine at the temps you are seeing. With a 50/50 water/ethylene glycol coolant mixture the boiling point is around 265 deg f. I believe the coolant is probably boiling inside areas of the waterjacket when you reach the 250 to 260 range on the gauge. This starts creating hot spots and vapor pockets. This can result in damage to internal engine components. The temp sensor is in the front of the intake manifold and the rear head and block area are probably even hotter then the gauge indicates. Once the cooling system gets to a temperature where vapor pockets are forming it can create the condition where areas of the heads or block are not being cooled even though coolant is flowing through the system. The vapor pockets prevent the coolant from contacting the surface areas and it doesn't take long for damage to occur. I have had pistons deformed as a result of this situation. The 401's are less forgiving of this condition than the 360's so at least that is in your favor.
Do you have an overflow tank? If not you are probably loosing coolant which makes the situation worse.
Are you getting much engine knock at the hot temps?
Does the transmission line run through the radiator tank? If so one thing you can do is delete the in-tank cooling loop and use an external tranny cooler. That way you won't be adding the transmission heat to the radiator.
Make sure the pump inlet hose isn't collasping as fredws pointed out. Are you running a 50/50 mix? Do you have a fan shroud? The fan clutch has already been mentioned. Is it working correctly? You could temporarily replace it with a spacer and see if that fixes the problem.

The basic answer from fredws of not enough coolant flow though the system or cooling air flow through the radiator is the first place to look.

[ September 02, 2002, 10:01 AM: Message edited by: Wesdog ]

[dws]

Dan - I recently had to replace the 727 in my 90GW and can give you some ideas on prices here in PA, but lets hope you don't need them. I have to say that your problem is much different than the problems I had when my transmission was going and I found the 727 to be pretty sturdy because it lasted for quite a long time after I started having problems (although it took me a long time to realize it was a tranny problem).

Anyway, local shop quoted $1,250 for local rebuild of my tranny including all labor to remove and reinstall. Also, quoted $1,510 to install a Jasper built 727 with a 3-yr 75,000 mile warranty (again including all labor etc...). I went with the Jasper because it is my daily driver and did not want to lose it for up to 2 weeks. I also spent a little more and had them replace that darn rear seal at the same time. They did a great job and the tranny is now silky smooth again but, alas, I am much poorer.

Dave
90GW (no longer leaving puddles of oil)
65Wag

[FSJ Thing]

Um.. what about the pressure-temperature being directly related, meaning that increasing the pressure on the engine side of the thermostat increasing the tempurature of the coolant on the engine side of the thermostat, and by reducing the pressure on the radiator side of the thermostat do the opposite, thus negating both of these factors. Also the molecular friction of the centrifical water pump pumping a percentage of the same coolant due to the back pressure caused by the thermostat adds to the heat in the engine as well and the increased resistance of trying to pump fluid through the thermostat. Also, if the coolant isn't loosing as much heat per given unit of measure, because more units of measure are traveling through the radiator in the same amount of given time, doesn't this mean that each given unit of measure of coolant picks up less heat in the water jacket for the same reason? Then wouldn't this negate both of these factors, meaning that less restriction, causes less friction, and thus less internal molecular kinetic energy? So a thermostat is just to keep an engine above it's lower temperature paramitter, but I don't see how it keeps it from exceeding it's upper temperature peramitter. O.K. I think I need another beer.

[krob725]

you could rebuild the trans yourself and save alot of money. try www.bulkparts.com (http://www.bulkparts.com) i have not used them but they seem to have good prices. i usually buy parts here in town at the same place all of the trans shops buy their's. you should be able to rebuild it for about $100.00 as long as you don't need too many "hard" parts. a rebuild kit with "steels" and a rebuilt converter should be enough. even if you got new bands and a new pump, you should still be under $200.00

good luck
krob725

[Dan G]

Thanks guys, esp krob725, I'll check out the link and let you guys know what I eventually end up doing.

[reddog]

Wagonstyne touched on the question I would have about the higher flow being better to cool the motor theory. If the coolant is not absorbing the engine heat well (at high flow) then it has little heat to transfer out of the system via the radiator.

All the thermodynamics aside, without a thermostat the motor runs too cold and that is bad for the engine and emissions. It will also negatively affect proper operation of the CTOs.

The system is designed to use a thermostat and if you are overheating removing the thermostat is not the fix. Sounds like after checking off everything on the list for cooling problems a electric fan may be in order due to the plow blocking the airflow as previously mentioned.

Kerry

[reddog]

Originally posted by Wesdog:
EDITED FOR LENGTH - The LT1's system has been re-designed so the radiator is on the low side of the system and not subject to high pressure. The only reason you even need a restrictor is to hold the gasket in place for the water neck.I thought the idea of reverse flow cooling was using the "just cooled" coolant to remove the heat from the place where the most of it is generated - the heads.

Kerry

[Marvin Gates]

In the summer put a 160 thermostat in, and in the winter put in a 195, and forget all the lessons. Although it it fun to see you guys argue about very simple problems. MG :D :D :D :cool:

[Jerk]

ok, so here's my take on the subject of high flow versus low flow: in order for a higher gpm flowing system to be optimal in cooling, there must also be a higher degree of air flow through the radiator or better heat dissapated material that the radiator is constructed of or more radiator for the same amount of air to flow through- meaning instead of a 2 core, possibly a 3 core or 4 core radiator or more fans on the 2 core radiator...I mean its all connected right, if you change one you gotta change the other too, right? in order to get the best efficiency from the change, i mean.

[Wesdog]

Originally posted by reddog:
I thought the idea of reverse flow cooling was using the "just cooled" coolant to remove the heat from the place where the most of it is generated - the heads, KerryKerry, That is exactly correct. The reverse flow cooling is designed to cool the heads first. But that is a totally different cooling system design than the AMC engines. It has the same basic components but they are configured very differently. I have a reverse cooled LT1 engine in another vehicle and really like the reverse cooled system design. Allows the use of 10:1 compression using 87 octane fuel.
Also, the theory of the coolant not absorbing engine heat due to a high flow system is just plain wrong - it doesn't work that way. However, without good airflow through the radiator it matters little if the flow is low or high - it's not going to do a good job of removing heat from the engine.

As far as the problem at hand with the AMC 360 running hot - I still recommend putting a high flow thermostat in to allow more total flow through the system. It won't hurt and is a cheap way to keep the engine at the desired minimum temp but still get better flow.

I never heard if there is a fan shroud on Dan's 360 or not and if the thermal fan clutch is fuctioning correctly. An electric pusher fan sounds like a good idea also.

[ September 01, 2002, 10:53 PM: Message edited by: Wesdog ]

[reddog]

WD,
1. I understand what is involved in a reverse flow system. Vettes have had it for how long now? Reverse flow makes too much sense. Like so many other things we are stuck with the caveman auto engineering. I didn't say (or mean to insinuate) that AMC ever did such a thing or that it would be needed on any motor in a 4X4.

2. As I read your post on the theory of the amount of heat transfered vs the coolant flow makes total sense. But what I don't understand is how that doesn't apply to getting heat from the motor into the coolant. Since your using the same medium (coolant) to move the heat the only difference in the amount of heat transfered at any givin coolant flow is the ability to xfer it from cast iron to coolant vs coolant to brass (or aluminum). Since the coolant/cast iron area in a 360 is roughly the same in any 360, the discussion was about different flow rates being able to transfer BTUs. How does this not apply to getting the heat INTO the coolant?? Taking into account of course the different metals contacting the coolant meaning that of course X area of an aluminum radiator will transfer more BTUs than the same area of a cast iron block/heads.

Of course "common" sense says that a more efficent radiator, better flowing thermostat, water wetter, more air flow etc will help to resolve overheating problems assuming that there is nothing "failing" on the cooling system. I think most agree about that.

Kerry

[reddog]

Originally posted by Marvin Gates:
In the summer put a 160 thermostat in, and in the winter put in a 195, and forget all the lessons. Although it it fun to see you guys argue about very simple problems. MG :D :D :D :cool: We are "discussing" :D I run a 180 thermostat and with the 3 row radiator I have not had any problems - knock of fake wood paneling....

Kerry

[bigchief79]

Are you running the stock cat? I had a similar problem. My chief ran hot and wouldn't shift into 3rd gear. Got to checking and the cat was stopped up.

[Wesdog]

Originally posted by reddog:
WD,
1. I understand what is involved in a reverse flow system. Vettes have had it for how long now? Reverse flow makes too much sense. Like so many other things we are stuck with the caveman auto engineering. I didn't say (or mean to insinuate) that AMC ever did such a thing or that it would be needed on any motor in a 4X4.

2. As I read your post on the theory of the amount of heat transfered vs the coolant flow makes total sense. But what I don't understand is how that doesn't apply to getting heat from the motor into the coolant. Since your using the same medium (coolant) to move the heat the only difference in the amount of heat transfered at any givin coolant flow is the ability to xfer it from cast iron to coolant vs coolant to brass (or aluminum). Since the coolant/cast iron area in a 360 is roughly the same in any 360, the discussion was about different flow rates being able to transfer BTUs. How does this not apply to getting the heat INTO the coolant?? Taking into account of course the different metals contacting the coolant meaning that of course X area of an aluminum radiator will transfer more BTUs than the same area of a cast iron block/heads.

Of course "common" sense says that a more efficent radiator, better flowing thermostat, water wetter, more air flow etc will help to resolve overheating problems assuming that there is nothing "failing" on the cooling system. I think most agree about that.

KerryKerry, I'm glad you mentioned we are just discussing cause that's all I'm doing and also trying to help Don.

Item 1. I never thought you were infering any AMC engines are reverse cooled. And yes, the reverse cooled LT1 (and the upgraded LT4 to a limited extent) was in Y-bodies, F-bodies and B-bodies for 5 to 6 years if I remember correctly. I have one. It's a good design for any engine cooling system. As I understand it, GM would probably be using it in the LS1 except they don't own the patent on the LT1 block reverse cooling design, didn't pay the patent owner the royalties they agreed on and are in a prolonged litigation over this.

Item 2: At least the same amount of heat is transfered in a higher flowing system as opposed to a lower flowing system and I still think the higher flowing system has a greater efficiency than the lower flow. That follows how mechanical waterpumps work and why they work. Lower flow when less heat is generated, higher flow when the engine is producing more waste heat. They pump at a rate proportional to the rpm of the engine up to the flow and pressure capacity of the system. The higher the RPM, the more fluid the impeller pumps through the system - up to a point.
If you are only looking at the heat absorbed in a single gallon of coolant flowing through a 30 gpm system vs a 10 gpm system, than you are correct: the temp rise due to the heat absorbed by a given gallon of coolant in a 10gpm system will be greater because it's in the engine longer and the heat released by that gallon when it travels through the radiator at the slower rate will be greater assuming a static amount of airflow through the radiator. But that is not right way to look at it because you have to consider how many BTU's per minute are being transfered from the coolant into the surrounding air flowing through the radiator. As you raise the flow rate you move the coolant through the engine faster and the total amount heat absorbed and radiated by the total GPM amount of coolant that has flowed stays at least the same or, as I believe, increases. But since that same gallon is exposed to heat and potential hot spots in the heads and block for a shorter time before entering the radiator to release some of that heat, the potential for a vapor pocket to form in the engine due to localized coolant boiling and vaporization is less. That is the main reason the higher flow controls the temperature better and is also safer for the engine.
Example: Say that same 1 gallon of coolant in a 10gpm system reaches 200 degf at the engine cooling outlet and cools to 160 before being pumped through again. Under these conditions increasing the flow won't do anything because the 195 degf thermostat will start to close and limit flow to maintain the operating temp. But as the system thermal load increases due to greater engine heat output for any number of reasons, or the cooling capacity decreases due higher outside air temp or less air flow across the radiator cooling fins or both, the temperature of the coolant entering and exiting the engine starts to rise. Once the temp is above the t-stat set point the thermostat will fully open. Now the flow restriction is at it's minimum and the flow rate is only varied by engine rpm which controls the pump impeller speed and resulting gph flow through the system. The flow is limited by the pump impeller design and speed and also by any restriction in the system such as that low flowing stock thermostat and/or blocked coolant passages in the engine and radiator or a collasped hose. There are areas in the engine that are hotter than others and so there is more localized heating of the coolant in certain areas. A 50/50 coolant mix at 15 psi has a boiling point of about 265 degf. Inside the engine when the coolant reaches that temp it boils and creates vapor. Once that happens there is effectively no further heat absorbed by the vaporized portion of the coolant until it recondenses back to a liquid. Small amounts of vaporization are normal and not a problem as the vapor is pushed out of the engine to the radiator where it recondenses back to a liquid. But when the overall engine temperature rises and approaches the 265 degf temp it starts to create vapor pockets within the engine that can prevent the liquid coolant from contacting these hot spots. As a result these areas get hotter and the vapor pocket spreads and doesn't get removed from the engine cooling passages. This also causes the pressure to rise in the system and will eventually overcome the pressure cap and expel coolant from the system which lowers the cooling capacity and makes the situation worse. This situation creates a chain reaction within the cooling system and will overheat the engine unless something changes such as the thermal load on the system or the cooling air temp/flow across the radiator. As the coolant flow increases the ability of the coolant to remain in a liquid state increases because it is exposed to less heat before exiting the engine.

Anyone wishing to correct my explaination go ahead, I am willing to listen and learn.

To help your engine cooling system work correctly to control the engine operating temperature you can do a few things to increase the flow rate: Install a radiator with more cooling surface area and lower flow restriction.
Use a high flow thermostat also called a 'Total Flow' thermostat. Install a higher volume waterpump - this is a pump with a plate welded onto the timimg case side of the impeller to increase the impeller's efficiency. (Both the high flow thermostat and higher volume pump are acceptable for our cooling system pressure limitations because the engines don't operate above 4500 rpm, at least mine doesn't).
None of this will help much if your engine cooling passages are blocked, the fan is not working properly due to a bad fan clutch or lack of a correctly designed and positioned fan shroud, or if the cooling air is blocked/restricted from flowing through the radiator.

Problems with overheating can be worse in stop and go traffic because of the low water pump flow and cooling fan speeds at low rpms. This is where electric cooling fans are very helpful because they aren't driven by the engine rpm. A high volume water pump also helps in this condition as does a high flow thermostat. If you can find a smaller diameter waterpump pulley that will also help low rpm cooling flow.

Checking the cat convertor is a good suggestion. If it is restricted it will lower the amount of heat the exhaust system expels from the engine and affect the engine performance also.

I I hope this was helpful to someone.

[ September 02, 2002, 07:45 PM: Message edited by: Wesdog ]

[Nobby]

Whilst we're on the subject has anyone used the additive for coolant systems that are advertised as helping in higher temp situations such as towing etc. There are several brands on the shelf and you add it in addition to the water/antifreeze mix. Unfortunatly I cannot recall the brand names right now.
Any good or just another no good miracle cure in a bottle?
Anyone running a lube oil cooler to good effect?

[reddog]

Welcome Nobby! I have run Redline Water-Wetter in the past and found that it helps some. No miracle fixes though. A good oil cooler would be helpful but my concern is the lack of a highflow oil pump for thw 360s. I have seen highflow pumps for some Buick V6s (which have the same type of oil pump) but none for the AMC. We need to get somebody who would machine a set of oil pump gears for us ... :D

Kerry